The present invention relates to net-like structures, and more particularly to a plastic net composed of composite filaments made up of two or more different plastic materials to provide the net with rip resistant properties.
It is known to extrude plastic nets by means of relatively rotating or reciprocating die members. These die members are provided with a plurality of orifices from which the filaments of the net are extruded. When the orifices of one die are immediately adjacent the orifices of the other die, the filaments from the two dies are fused together to form the interstices or crossings of the plastic net. If only two dies are used, a two-layer net will be produced. However, it is also known as shown in U.S. Pat. No. 3,227,124 to Anderson et al, for example, to provide a die head capable of producing a three-layer net. See also U.S. Pat. No. 3,123,512. The plastic nets produced in this manner have many diverse applications from produce bags and other packaging applications to netting for protecting agricultural crops from birds.
In my copending application Ser. No. 270,659, filed June 5, 1981 now U.S. Pat. No. I disclose a helical net-like structure comprising at least two crossing layers, the first layer being a plurality of first helical filaments, the axes of which are parallel and the second layer being a plurality of second helical filaments, the axes of which are parallel but intersect the axes of the first helical filaments. The first and second helical filaments are fused together at each point of intersection. To make this net-like structure, conventional net making equipment is used with the modification that each orifice of both relatively rotating or reciprocating dies is fed with two different plastic materials characterized by having different properties of contraction and orientation. One material may be a synthetic elastomeric rubber-like material such as butyl rubber, and the other a plastic material, such as polypropylene or polyethylene. The net is extruded from the die head in the usual manner, and then the filaments are oriented by stretching and releasing to cause the filaments to contract into helices.